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Discussion Starter · #1 · (Edited)
New to the little 4 strokes, but not to wrenching.

I picked up a bearly used Dolmar PB251.4 leaf blower. Has no compression.

Took off the rocker cover and rolled engine over, and valves not working.

Took apart a little further and found the cam gear in 2 pieces-should be 1. the gear came unglued from the cam.

I have ordered a new cam gear, but when I get wround to installing. how do I set the valve timing?

There is a mark on the high part if the cam lobe, but where is the mark for the crank?

I was thinking of setting the piston at TDC, and lining upo the cam mark with a mark on the crank case.

Is this a good plan, or is there a better (correct way) to do it?

And How much spark should this little guy have?

Thanks

Mike

And please excuse if this is not the correct place for this question.
 

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Discussion Starter · #2 ·
Well, I JB welded the 2 pieces of timing gear/cam together and let it cure over night.

This morning, I put it together-my theory on valve timing works, don't know if it's right, and fired on the first pull.

ran it for 5 min, shut it down. Went back 1/2 hr later, fired up and blew leaves for a half hour.

The little devil runs great and I think the valve timing is right on the money.

Almost hate to tear it down when the new gear comes. mMight just wait until the JB weld gives out.:D
 

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If your timing procedure is not correct and you find the correct, please share. I tried to find info but d/n. Old School was usually a mark on Crank and Cam to match. As you said, I feel you are on or close with the performance results.
 

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Discussion Starter · #4 · (Edited)
There are 2 small holes in the recoil engagement (peice of tin on the end of the crank.

I set the piston to top dead center, then lined up the mark on the cam to the center of one of the inspection holes. Just like I did for the old 235 6 cyl chev engines. (only they used a ball on the flywheel and a pointer on the bell housing).

rolled it over by hand very carefully as not to bend little valves or push rods.

Pushed the primer bulb several times and gave it a good pull. Popped right off, but I took it off choke too soon, so I set it at 1/2 choke and gave it one more. Popped right off.

been using it off and on yestgerday and today. All it takes is one pull w/ful choke. Let it warm up and off choke.

Best starting small engine I ever had.

Don't know if this is the "book" method, but it worked great.

Next up is a Poulan Pro PPB430VS. I beleive that it's ign. coil is toast, as are most of them.This guy is mint, just full of dust.
 

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Troubleshoot the Pro and get back! Since the 70s I’m not up to date vs dealing with basics, Fire/Fuel/Compression.
 
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